Tagatose has a natural sweet taste which is hardly distinguishable from sucrose and has physical properties similar to sucrose. However, ingested tagatose is not well absorbed in the small intestine and thus has a minimal impact on blood glucose level. Further, tagatose is a low calorie sweetener having about 30% the calories of sucrose. In addition, tagatose has a prebiotic effect that promotes growth of beneficial lactic acid bacteria through fermentation by intestinal microflora.
Only about 20% of ingested tagatose is absorbed in the small intestine and the remaining 80% fraction of tagatose reaches the large intestine where the intestinal microflora lives, and selectively promotes the production of lactic acid bacteria, thereby producing short chain fatty acids. Particularly, tagatose has a prebiotic property capable of producing large amounts of butyrate (up to 50% of the total short chain fatty acids) which can prevent colon cancer. Furthermore, tagatose is a natural sugar having a low-calorie value of 1.5 kcal/g and has attained GRAS (Generally Recognized As Safe) status under the U.S. Food and Drug Administration, thereby permitting use as a functional sweetener in foods, beverages, health foods, diet additives, and the like.
However, tagatose is not often found in nature and is a rare sugar present only in small amounts in dairy products and some plants. In order to use tagatose as a low-calorie and functional sweetener, it is essential to develop a method for mass production of tagatose from inexpensive raw materials.
Tagatose has conventionally been produced by isomerization of galactose. In order to economically afford galactose, studies have been carried out to develop various raw materials containing galactose, methods for attaining galactose and methods for producing tagatose using the raw materials. Lactose has been used as the most representative raw material for tagatose. However, the prices of lactose or lactose-containing products show a unique price pattern of repeating fall and rise due to various factors such as amounts of raw milk produced according to weather, demand for powdered milk, changes in lactose amount consumed in developing nations, and the like. Such price fluctuations in the raw milk market make the stable supply of raw materials for producing tagatose difficult. Accordingly, there is a need for a new method for producing tagatose using common raw materials (glucose, sucrose, fructose, and the like).
Korean Unexamined Patent Publication No. 10-2009-0125004 discloses a method for producing galactose by epimerization of glucose. Korean Unexamined Patent Publication No. 10-2006-0125971 discloses C3-epimerization of ketohexose. However, both documents fail to disclose a method for producing tagatose through C4-epimerization of fructose.